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blakdeath
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Joined: 21 Sep 2012
Posts: 462

PostPosted: Thu May 16, 2013 5:06 pm    Post subject: problems booting from usb Reply with quote

I have install gentoo on my flash usb.
grub loads up just fine, I do however get the following kernel panic:
VFS: cannot open root device sdb1 or unknown block(0,0): error
please append a correct root= boot option
here are the available partitions:
<listing of my hard disk, not my usb>
I have used genkernel to create an initramdisk, and the system boots fine, but I'd rather boot without one(for educational purposes), which means the problem is with my kernel config, somehow the PC cannot see /dev/sdb1 when it starts loading
here's my .config file:
http://pastebin.com/HJDeniQt

thanks
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NeddySeagoon
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Joined: 05 Jul 2003
Posts: 31711
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PostPosted: Thu May 16, 2013 5:38 pm    Post subject: Reply with quote

blakdeath,

You need to build your kernel so it works without the aid of an initramfs or you need to edit the init script in the initramfs.

The problem is that the kernel tries to mount root, which is on USB before the USB subsystem is started, so its doomed to fail.
Thus you need to tell the kernel to wait for a few seconds. Add rootdelay=7 to your kernel line.
However, when you use an initramfs, the wait will be in the wrong place ... it will wait before mounting the initramfs, which is not what you want.

Fixing your kernel and throwing away the initramfs is the simple approach. You can still use genkernel for most of the work if you really want to.
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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blakdeath
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Joined: 21 Sep 2012
Posts: 462

PostPosted: Thu May 16, 2013 6:37 pm    Post subject: Reply with quote

perfect, that solved the problem and I understand what just happened there
thanks alot Neddyseagoon
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